Actuating means for shoe drum brakes



April 12, 1966 J. 1'. DunLEY 3,245,501

ACTUATING MEANS FOR SHOE DRUM BRAKES Filed June 4, 1964 4 Sheets-Sheet 1 IFT.

April l2, 1966 J. T. DUDLEY ACTUATING MEANS FOR SHOE DRUM BRAKES 4 Sheets-Sheet 2 Filed June 4, 1964 April 12, 1966 J. T. DUDLEY ACTUATING MEANS FOR SHOE DRUM BRAKES 4 Sheets-Sheet 3 Filed June 4, 1964 April 12, 1966 J. T. DUDLEY 3,245,501

ACTUATING MEANS RoR sHoR DRUM BRAKES Filed June 4, 1964 4 Sheets-Sheet 4 United States Patent M ACTUATING MEANS FR'SHGE DRUM BRAKES .lohn Trevor Dudley, Brewood, England, assignor to Girling Limited, Tyseiey, England Filed .lune 4, 1964, Ser. No. 372,508

Claims priority, application Great Britain, June 8, 1963,

22,946/ 63 11 Claims. (Cl. 18S-106) This invention relates to improvements in shoe drum brakes of the kind in which arcuate shoes mounted on a ystationary back-plate are adapted to be separated to bring them into engagement with a rotatable drum. D

According to our invention, in a brake of the kmd set forth a cam or equivalent means for separating the shoe ends is actuated by a cable which is carried r-ound a quadrant pivotally mounted on the back-plate in such a manner that the movement of the cable in the actuation of the brake is accommodated by angular movement of the quadrant and there is no relative sliding movement between the cable and the quadrant,

Wear of the cable is thus reduced and the cable is not subjected to the flexing to which a cable carried round a pulley is subjected.

The quadrant can be pivotally mounted on the inner face of the back-plate in which case the cable is brought in through an opening in the back-plate and carried round the quadrant. Alternatively the quadrant can be pivotally mounted in a recess formed in the outer face of the black-plate and the cable is carried round the quadrant and then brought in through an opening 1n the end of the recess adjacent to the cam.

A shoe drum brake of the `duo-servo type incorporating a quadrant and cam arrangement in accordance with our invention is illustrated by way of example in the accompanying drawings in which:

FIGURE 1 is an elevation of a portion of a brake showing the cam, the adjacent ends of the shoes, and the quadrant;

FIGURE 2 is a section on the line 2--2 of FIGURE l;

FIGURE 3 is an elevation of the cam and cable incorporated in FIGURE l;

FIGURE 4 is a perspective view of the brake similar to that illustrated in FIGURE 1 and showing in greater detail the form of the quadrant;

FIGURE 5 is a plan of the brake illustrated shown in FIGURE 4 with the shoe adjacent to the quadrant removed; Y

FIGURE 6 is an elevation of the earn; and

FIGURE 7 is a plan of FIGURE 6.

In the brake illustrated 1t), 11 are opposed complementary arcuate brake shoes mounted on a stationary back-plate 12, The shoes are of T section having radial webs 13 and carrying friction linings 14 adapted to be brought into engagement with a rotatable drum (not shown), the shoes normally being held out of engagement with the drum by return springs connected across the shoes of which one of the springs is shown at 15.

For normal service braking the shoes are separated at one end by an hydraulic actuator comprising a doubleended hydraulic cylinder 16 in which work opposed piston 17 acting on the shoes through thrust members 18. Each thrust member is in articulated engagement at one end with its adjacent piston and in articulated engagement at its other end with the web of its adjacent shoe. The other ends of the shoes are articulated together or coupled by a conventional floating thrust member so that when the brake is applied the leading shoe tends to rotate with the drum and applies a thrust to the trailing shoe which fulcrums on an anchor pin 19 fixed on the back-plate between the shoes at their actuated ends, the

3,245,5'5l Patented Apr. 12, 1966 ICC anchor pin being located radially outwards from the hydraulic actuator. The thrust member is adjustable in length to compensate for wear on the friction linings.

The shoes can also be separated mechanically to apply the brake by operation of a cam 20 positioned between the shoes at the ends adapted to be actuated by the hydraulic actuator. In the arrangement illustrated the cam 20 integral with a lever 21 is mounted for angular movement on an eccentric spigot portion 22 extending outwardly from the anchor pin 19. The cam is secured on the spigot on the outer side of the shoe webs -by a washer 23 and a snap-ring 24 engaging in an annular groove. in the outer end of the spigot portion. The cam has a slot 25 which receives the spigot and integral with the cam on diametrically opposite sides of the slot is provided a pair of inwardly projecting lugs 26 which engages between raised abutment portions 27 welded to the ends of the adjacent shoe webs on their outer sides. Alternatively the abutment portions 27 may be integral with the shoe webs. The circumferential length of the lugs 26 on the cam is less than the diameter of the anchor pin 19 so that when the brake is applied by the hydraulic actuator the torque on the brake shoes is taken directly by the anchor pin.

To the free end of the cam lever 21 is secured a cable 28 which is brought in through an opening 29 in the back-plate and is received in a peripheral groove 3i) in a quadrant 31 pivoted on a pin 32 between lugs 3.3 weldm or otherwise secured to the inner face yof the back-plate. The cable is substantially at right angles to the cam lever and is secured in the peripheral groove in the quadrant by the friction between the quadrant and the cable. cured to the quadrant by crimping or closing in the sides of the groove onto the cable as shown at 34 so that when the cam is moved angularly by the cab-le there is no relative sliding movement between the cable and the quadrant and wear on the cable is reduced. The opening 29 in the back-plate is of substantial diameter to accommodate changes in the angular position of the quadrant and the opening is protected by a rubber or other boot 35 (FIGURE 3) through which the cable passes.

In another arrangement, the cable 2S is secured to the quadrant 31 by collars xed on the cable and which abut against opposite ends of the quadrant and prevent relative movement between the cable and the quadrant taking place.

Where insuflicient space is available for positioning the quadrant inside the housing the back-plate can be lformed with a recess extending into the housing to a depth substantially equal to the distance between the backing plate and the outer end of the spigot. The quadrant is pivotally mounted in this recess on the outer side of the backing plate and the cable is passed from the quadrant to the cam lever through an opening in' the upper end of the recess.

To apply the brake mechanically the cam 20 is moved angularly about the spigot portion 22 of the anchor pin 19 and the adjacent shoe ends are moved apart. The leading shoe applies to the trailing shoe a trust urging it into engagement with the anchor pin and the cam, due to its slot 25, has a limited circumferential movement relative to the spigot to accommodate the small circum- :ferential movement of the shoes which takes place according to the direction of rotation of the drum which determines which shoe acts as the trailing shoe.

It will be appreciated that when the brake is applied hydraulically as described, as the hydraulic actuator acts on the shoe webs 13 and the torque on the shoes is taken by the anchor pin 19 through the shoe webs, both the applying force and braking torque act in the same plane.

Alternatively, as illustrated, the cable is se-V' aeaaaoi However when the brake is applied mechanically, although the torque on the shoe is taken by the anchor pin 19 directly through the shoe webs 13, the applying force due to the co-operation of the lugs 26 on the cam 20 with the raised abutment portion 27 on the shoe webs acts on the shoes through a plane offset outwardly from the shoe webs by arranging that the cam can move angularly about the outwardly projecting spigot portion 22 of the anchor pin. This permits the lugs on the cam to be disposed substantially within the projected area of the ac-hor pin.

This is of particular advantage in brakes where there is limited radial space available between the anchor pin and the hydraulic actuator. Furthermore when the shoes are adjusted to compensate for wear on the friction linings by adjusting the length of the thrust member connecting the non-actuated ends of the shoes, the separation of the portions of the shoes co-operating with the anchor pin is not affected and hence the angular movement of the cam 29 to apply the brakes remains constant.

I claim:

1. An internal shoe drum brake comprising a rotatable drum, a stationary back-plate, opposed arcuate shoes mounted on said stationary back-plate and carrying the friction linings for engagement with said drum, said shoes having actuated ends and non-actuated ends, fixed abutment means engageable by at least one end yot one of said shoes, a cam located between said actuated shoe ends and rotatable about mounting means on said backplate to separate said actuated shoe ends and to apply said shoes to said drum, a quadrant separate from said cam, pivot means `on said back-plate independent of said cam mounting means and on which said quadrant is pivotally mounted, a cable carrie-d round said quadrant and connected at one end to said cam to actuate said cam to apply the brake, and co-operating means between said quadrant and said cable to prevent relative sliding movement between the cable and the quadrant whereby movement of the cable in the application of the brake is accommodated by angular movement of said quadrant about said pivot means.

2. An internal shoe drum brake as claimed in claim 1, wherein the back-plate has an inner face and an outer face, and said pivot means on which said quadrant is mounted is located on the inner face of said back-plate and said cable is brought through an opening in the back-plate and carried round said quadrant.

3. An internal shoe drum brake is claimed in claim 2, wherein the opening in the back-plate is protected by a flexible boot through which the cable passes.

4. An internal shoe drum brake as claimed in claim 1, wherein said means to prevent relative ysliding movement between said cable and said quadrant comprise friction between them.

5. An internal shoe drum brake as claimed in claim 1, wherein said means to prevent relative sliding movement between said cable and said quadrant comprise collars fixed on said cable and abutting against opposite ends of said quadrant.

6. An internal shoe drum brake as claimed in claim 4 1, wherein said quadrant has a peripheral groove in which said cable is received and in which said cable is secured by crimping the sides of the groove onto the cable.

7. An internal shoe drum brake of the duo-servo type comprising a rotatable brake drum, a stationary backplate, arcuate shoes mounted on said stationary backplate and carrying friction linings for engagement with said drum, each shoe having a radial web having an inner side adjacent the back-plate and an outer side, said shoes having actuated and non-actuated ends, oating means operatively interconnecting the non-actuated ends of said brake shoes, an anchor pin mounted on the back-plate between the actuated ends of the shoes and forming an abutment for one of said actuated shoe ends in the application of the brake of which the web of that shoe is adapted to engage with said anchor pin, an extension on said anchor pin remote from said back-plate, a cam rotatably mounted on said extension to separate said actuated shoe ends and to apply said shoes to said drum, raised abutment portions on the outer sides of the shoe webs at their actuated ends, and a pair o inwardly projecting lugs on said cam adapted to engage between said raised abutment portions to apply to the shoes in the application of the brake a force otlset axially and outwardly from the plane of the shoe webs.

8. An internal shoe drum brake as claimed in claim 7, wherein the extension on the anchor pin engages in an opening in the cam, and the opening permits the cam to move circumferentially in the application of the brake to accommodate circumferential movement of the shoes accordin to which shoe engages the anchor pin when the brake is applied.

9. An internal shoe drum brake as claimed in claim 7, and further including means for applying the brake hydraulically independently of said cam comprising an hydraulic piston and cylinder assembly located between the actuated shoe ends at a position disposed radially inwards from the cam.

10. An internal shoe drum brake as claimed in claim 9, wherein the circumferential length of lugs on the cam is less than the diameter of theA anchor pin whereby when the brake is applied hydraulically the torque on the brake shoe is taken directly by the anchor pin and none of the torque is taken by the cam.

11. An internal shoe drum brake as claimed in claim 7 wherein the extension on which the cam is mounted is eccentric with respect to said anchor pin and the axis of the extension is located radially inwards from the axis of said anchor pin.

References Cited by the Examiner UNITED STATES PATENTS 1,936,899 11/1933 Bendix et al. 18878 1,976,420 10/1934 Taylor 18S-78 2,064,617 12/1936 La Brie.

2,111,503 3/1938 Axtmann 18S-78 X 2,167,706 8/1939 Berno.

DUANE A REGER, Primary Examiner. 

7. AN INTERNAL SHOE DRUM BRAKE OF THE DUO-SERVO TYPE COMPRISING A ROTATABLE BRAKE DRUM, A STATIONARY BACKPLATE, ARCUATE SHOES MOUNTED ON SAID STATIONARY BACKPLATE AND CARRYING FRICTION LININGS FOR ENGAGEMENT WITH SAID DRUM, EACH SHOE HAVING A RADIAL WEB HAVING AN INNER SIDE ADJACENT THE BACK-PLATE AND AN OUTER SIDE, SAID SHOES HAVING ACTUATED AND NON-ACTUATED ENDS, FLOATING MEANS OPERATIVELY INTERCONNECTING THE NON-ACTUATED ENDS OF SAID BRAKE-SHOES, AN ANCHOR PIN MOUNTED ON THE BACK-PLATE BETWEEN THE ACTUATED ENDS OF THE SHOES AND FORMING AN ABUTMENT FOR ONE OF SAID ACTUATED SHOE ENDS IN THE APPLICATION OF THE BRAKE OF WHICH THE WEB OF THAT SHOE IS ADAPTED TO ENGAGE WITH SAID ANCHOR PIN, AN EXTENSION AN SAID ANCHOR PIN REMOTE FROM SAID BACK-PLATE A CAM ROTATABLY MOUNTED ON SAID EXTENSION TO SEPARATE SAID ACTUATED SHOE ENDS AND TO APPLY SAID SHOES TO SAID 